Osteoarthritis (OA) is the most common condition affecting older people today. It is the leading cause of disability among older people and its impact is projected to increase substantially with the aging of the U.S population (CDC, 1999; CDC, 2003). To date, 10 randomized trials of exercise interventions have been conducted among persons with OA. Although most report positive short-term outcomes at three months or less, only two have reported mixed findings on longer-term adherence and related outcomes at 12 or 18 months. This paucity of data on the maintenance of long-term exercise behavior among persons with OA indicates an urgent need for additional studies of issue. This study will use a multi-site randomized controlled trial with repeated measures to assess the comparative effects of two different ways of enhancing tong-term adherence to and benefits associated with participation in the evidence-based, Fit and Strong multi-component exercise intervention for older persons with lower extremity OA (Hughes et al., in press). We will recruit 600 persons to participate in the 8-week Fit and Strong program. At the conclusion of Fit and Strong, participants will be stratified by arthritis severity and randomized to either Negotiated Maintenance, in which individualized tailored adherence plans will be developed, or Mainstreamed Maintenance, in which participants will be mainstreamed into an ongoing facility-based program at each of four participating study sites. In addition, half of the participants in both maintenance arms will be randomly assigned to receive telephone reinforcement. We will use generalized estimating equations and random effects models to test the hypotheses that Negotiated maintenance participants will experience significantly greater levels of adherence to exercise at 2, 6, 12, 18, and 24 months, and significant improvements in self-efficacy for exercise, self-efficacy for exercise adherence, self reported and observed functional status, and psychosocial measures compared to Mainstreamed maintenance participants at 2, 6, 12, and 18 months.